update docs

Author: dglowinski

README.md

@@ -157,5 +157,8 @@ const pipeline = [
 
 Additionally there is a script to generate auxiliary config files, executed by `pnpm run generate-config`. Currently it fetches the list of supported [Pendle aggregators](./src/swapService/strategies/aggregators/sources/pendle/pendleAggregators.json) for all chains
 
+## Selecting providers
+Instead of fetching all quotes in a single call, which is as fast as the slowest provider's response, clients can send parallel requests with providers preselected in the optional `provider` query param. The endpoint `\providers` lists available providers per chain. The list is rarely updated so it can be cached on the client.
+
 ## Tokenlists
 The router relies on tokenlists for all swapped tokens. They can be fetched from `TOKENLIST_URL` or read from JSON files in `tokenLists` folder if the configuration is missing. Note the files are not updated currently. Please reach out on [Euler discord](https://discord.com/invite/pTTnr7b4mT) if you need access to the tokenlist endpoint.

src/swapService/strategies/strategyERC4626Wrapper.ts

@@ -287,8 +287,12 @@ export class StrategyERC4626Wrapper {
 
     if (!result.supports || !result.match) return result
 
+    // if the swap is between a vault and it's asset, which is handled directly,
+    // only proceed if the provider is not set (all providers) or it's the "custom" provider.
+    // Otherwise return an empty result, which will end the pipeline and return 404.
+    // Without this, the client would receive duplicate internal quotes
     if (this.isDirectSwap(swapParams) && !includesCustomProvider(swapParams)) {
-      result.quotes = [] // this ends the pipeline and returns empty results
+      result.quotes = []
       return result
     }